Current Issues Arising From Tuberculosis Screening With Interferon-Gamma-Release Assays (Igras)

A positive IGRA test does not always indicate a latent tuberculosis infection (LTBI); the prevalence of LTBI in the tested collective must be carefully considered in test interpretation. When IGRAs are performed repeatedly in healthcare workers (BiG), variabilities of test results (conversions and reversions of the respective previous negative or positive result) can be expected. Therefore only individuals for whom there is an established risk of being infected by Mycobacterium tuberculosis (M.tb.), i.e. significantly prolonged direct exposure to an infectious TB case, should be tested.Positive IGRA results alone do not reliably predict subsequent progression to active TB disease. According to the current body of scientific knowledge, IGRAs are not superior to the tuberculin skin test (TST) in the case of young children.